Rotary potentiometer brake



March 1965 w. 'r. HARDISON ET Al. 3,172,070

ROTARY POTENTIOMETER BRAKE Filed Aug. 28, 1962 2 Sheets-Sheet 1 FIG. 1.

, FIG. 2.

W/LBUR 7. Haw/50 R 61. MATH/50M March 1965 w. T. HARDISON ETAL 3,172,070

ROTARY POTENTIOMETER BRAKE Filed Aug. 28, 1962 2 Sheets-Sheet 2 INVENTORS W/LauR 7.' HARD/50M,

United States Patent 3,172,070 ROTARY POTENTIOMETER BRAKE Wilbur T. Hardison and Victor G. Mathison, Riverside, Calif., assignors to Bourns, Inc., a corporation Filed Aug. 28, 1962, Ser. No. 219,851 14 Claims. (Cl. 338-163) The invention herein disclosed pertains to rotary instruments such as variable resistors or otentiometers, of the types that are attached to and project from the front face of a panel, and more particularly the invention pertains to simple means for permitting ready arrestment or lockting and releasing of the rotary means such as the rotary housing that is actuated to change the adjustment of the instrument.

In a variable resistor device recently introduced to the market the operative components including a plural-turn helical resistance element are enclosed within a generally cylindrical shell that is rotatably supported upon stationary means comprising a flanged stud that is adapted for mounting in an aperture formed in a panel or console. The variable resistor is disposed at the front of the panel and may be adjusted by rotation of the shell which serves both as an adjusting knob and as a housing for protecting the other components of the resistor. Since in many instances a plurality of such variable resistors may be mounted in close juxtaposition, or closely adjacent to other devices that require manual adjustment or operation, there is likelihood of a hand of a technician, or a tool, coming inadvertently into contact with the knob or shell and accidentally rotating the resistor contact to an undesired position. Such accidental misadjustment is especially likely because of the ease with which the shell of the described device may be rotated, application of only a very light tangential force on the shell being sufificient to cause rotation.

The present invention provides an inexpensive readilyoperated brake device or means that permits an operator to secure or lock the rotatable shell or knob against rotation, or to release the shell for rotation. The brake device is so made that it occupies very little space beyond that small space required for the resistor, and so constructed that the operating member thereof can be readily applied to and removed from a variable resistor that is already in place atfixed to a panel. In the commercial form of the previously described variable resistor, a special anti-rotation washer is employed to prohibit rotation of the mounting stud in the aperture of the panel. The washer comprises first and second oppositely directed key members bent out from the body of the washer. The first key reposes in a small hole formed in the panel, and the second fits in a small hole formed in a stationary part of the body of the potentiometer, whereby relative rotation is prevented. In a preferred embodiment of the present invention the anti-rotation washer is slightly modified, without, however, appreciably increasing its cost, and it is used as one member of the brake device. The washer is cut away at one or more places at and adjacent its periphery to provide a corresponding number of resilient finger-like brake elements that are disposed closely adjacent to a frictional end surface of the rotary shell. Thus when the brake element or elements are pressed forwardly as by cam means, engagement with the frictional surface of the shell occurs, and the latter is arrested or frictiona'lly locked against rotation until the brake element or elements are released. Thus as may be evident, the washer or disc is furnished and sold as a normal hardware component of the variable resistor device, whether or not a brake or lock is desired, since the added cost is negligible and the space occupied is exactly the same.

For the purposes of accommodating the present invention the panel-contacting flange of the stud is formed with a step of reduced diameter to provide an annular step or seat upon which brake-operating means is mounted. The brake-operating device is arranged for limited rotary or rocking movement on the seat formed on the stud, and is provided with one or more cam elements each of which is disposed and arranged for cooperative action with a respective brake element of the washer. The brakeoperating device, hereinafter referred to as the brake actuator solely for convenience, is preferably and in an exemplary form shaped as a modified C-shaped retainer ring with one or more operating wings or limbs arranged to be manually operated by the technician or operator. Due to its structural character the actuator may be pressed or snapped into place upon the seat on the flange of the stud, where it holds itself by spring action in the manner of a common contractile retainer or C-ring. The operating wing or wings of the actuator are formed and disposed for easy movement by the technician to or from the position or attitude in which the cam-element means presses the brake-element means forwardly into frictional engagement with the sleeve or knob of the instrument. Thus when rocked or rotated to engage the brake or lock, the cam-element means of the actuator force the brake-element means into engagement with the rotary shell or sleeve of the potentiometer and when rocked reversely the cam-element means move away from the brake-element means and the latter, by their inherent resilience, spring rearwardly away from the sleeve to release the latter for free rotation. The actuator may be very inexpensively produced as a stamping punched by die means from a sheet of thin resilient metal; and due to its thin structure it adds only a negligible amount to the space requirements of the instrument.

The preceding brief general descriptive sketch of the invention makes it evident that it is a principal object of the invention to provide improvements in instruments such as rotary variable resistors of the aforementioned type, in which the instrument is adjusted by rotation of a shell or the like.

Another object of the invention is to provide a simple brake or arrestment device for a rotary instrument of the type mentioned.

Another object of the invention is to provide an inexpensive arrestment device for a rotary instrument of the. type mentioned.

Another object of the invention is to provide an easily assembled brake device for a rotary instrument of the class noted.

Another object of the invention is to provide a brakeoperating device that is easily applied to and removed from a panel-mounted potentiometer or like instrument.

Other objects of the invention, and advantages thereof, will be made apparent in the appended claims and by the following description of a preferred form of the invention as illustrated in the accompanying drawings that form a part of this specification.

In the drawings:

FIGURE 1 is a front or face end view of a plural-turn helical-element variable resistor device mounted at an aperture in a panel and disposed forwardly of the face of the panel, with a preferred exemplary form of the invention applied to the resistor, and :a portion broken out to show a detail;

FIGURE 2 is a side view of the structures illustrated in FIGURE 1;

FIGURE 3 is a view partly in section and with parts broken away, illustrating on an increased scale the relative dispositions of brake device components shown in FIGURE 2, the sectioned portion being taken as indicated by line 33 of FIGURE 1;

FIGURE 4 is a view in section showing brake device components, the view being taken as indicated by line 4-4 of FIGURE 2 and illustrating the components in brakeolf or released attitude;

FIGURE is a view similar to FIGURE 4 but illustrating the components in the brake-on or engaged attitude;

FIGURE 5a is a fragmentary detail view illustrating engagement of a cam device with a brake element and engagementof the brake element with a rotatable part of a resistor;

FIGURE 6 is a view of variable resistor parts and brake parts in disassembled array, with parts removed or broken away;

FIGURES 7 and 8 are views illustrating a modified form of brake device or actuator adapted for alternative use with components of the preferred form of the invention, in instances where otentiometers are disposed in close array; and

FIGURE 9 is a fragmentary view illustrating a second or alternative disposition of a key relative to a brakeactuating device.

Referring first to FIGURES 1, 2 and 3, there is depicted a portion of a flat sheet-like panel P having an aperture A at which a variable resistor R is mounted on the panel. The variable resistor comprises a support means or device, the rear end portion of which is in the form of an externally threaded stud B. The stud comprises a flange F adapted to be drawn against the front face of the panel P by a nut N with interposition of a conventional washer W. The labeled components thus far described are per se known in commerce. The variable resistor R comprises a rotatable member in the form of a knob, and herein shown as a rotatable shell S that is supported for rotation upon stationary means comprising stud B. Variation of the resistance exhibited between the terminals (not shown) of the resistor R is effected by rotation of the shell S. The shell, as is indicated in FIGURE 6, has a cylindric configuration and has an annular rear face or surface Sf that is disposed in a plane. The stationary means upon which the shell is rotatable includes a body member M that is rigidly secured to stud B. To secure the stationary structure of the variable resistor in a fixed position and attitude relative to panel P, an anti-rotation washer Q is interposed between the panel and member M. Washer Q is formed with a first key member Qr (FIG- URE 6) that extends rearwardly from the general plane of the washer and engages in a hole H (FIGURE 1) formed in panel P; and the washer also is formed with a second key Qf that extends forwardly and engages in a keyway K (FIGURE 6) formed in body member M of the resistor. The washer has a central aperture that is dimensioned to fit closely upon the forwardly extending body of stud B, and thus, with key Qr engaged in the hole in panel P and key Qf engaged in keyway K, the stationary parts of the resistor are accurately positioned and held against rotation in aperture A. It will be understood that washer Q is disposed between flange F of the stud B, and body member M (as indicated in FIGURE 3), during assembly of the variable resistor. Other details of the construction of the instrument herein represented by variable resistor R are not deemed necessary to a full understanding of the present invention, and may be such as are illustrated and described in copending application Serial No. 119,608, filed June 26, 1961, and assigned to the assignee of the present application, and to which disclosure reference may be made if necessary.

For purposes of the present invention the aforementioned resilient anti-rotation washer (or a similarly disposed stationary resilient washer if washer Q is not used) is punched away as at It) to provide one or more resilient arcuate fingers or brake elements such as that denoted by the ordinal 12. Each brake element thus provided is resilient and is normally disposed in the general plane of the washer but is arranged and adapted to be deformed or forced forwardly into contact with the surface Sf of the rotatable shell S of the resistor. As is thought to be evident, shell S rotates around stationary member M. Also the diameters of washer Q and of shell S are preferably the same, and the radial width of element 12 is preferably approximately the same as that of surface Sf of shell S.

Formed from resilient sheet metal and adapted to be snapped over the reduced-diameter step F of flange F is the brake-actuating means or device 14 of the invention (FIGURES 4 and 6). As is indicated, device 14 has the general body configuration of a C-shaped retainer spring; and is thus adapted to be easily forced into position on a variable resistor mounted on a panel. It also is equally well adapted for easy removal from the resistor. The device comprises two depending stud-clasping limbs 14a, 14b, integral with and interconnected by an intermediate portion Mi, and at least one wing portion 14w formed and disposed for access and rotation by a technician or operator. Preferably, and as shown, two such Wing portions 14w are provided. The intermediate portion 14i may be variously shaped, but conveniently may comprise a portion of radius greater than that of the sleeve S and hence visible above the rear of the potentiometer and bearing indications as shown in FIGURE 1. Further, in those instances in which the rearwardly projecting key Qr of washer Q is at the top as shown, the intermediate portion 14i may have a cut-out 14q to accommodate the key. It will be understood that key Qr may in some cases be at the bottom of washer Q, as indicated in FIGURE 9, in which case a cut-out 14q would be optional. However, the radial edges 14g, 14h (FIGURE 4) serve with key Qr as stops to limit rotation of device 14'. Normally, rotation in the brakeapplying direction is limited by the action of presently described cam means as the brake-element means are moved, but rotation in the brake-releasing or 01f direction is limited by action of one of the edges 14g, 1.411 and key Qr. It will be understood that use of the rotation stops is not necessary to full functional operation of the brake means; however, the stops aid in maintaining device 14 in a convenient and preferred operating orientation.

As is indicated in FIGURE 4, the depending limbs 14a and 14b are formed to be normally spaced apart a distance somewhat less than the diameter D of the step F of the flange, and the interior surfaces or edges of the limbs are curved to fit the step as indicated. Thus the device 14 may be snapped onto the step and will by inherent resilience maintain its position on the step or seat with the limbs clasping the stud and rotatable therearound.

Device 14 comprises suitable cam means for pressing the brake-element means into frictional engagement with the surface Sf. As illustrated, the cam means comprises one cam device for each brake element. Preferably each cam device is integral with the device 14 and is conveniently produced by a dimpling operation which deforms the metal and presses out an inclined ridge as indicated in FIGURE 6, to form a cam such as 14m or 14m. As indicated in that drawing, two such cams are provided, each of which rises forwardly from its base in the plane of the body of device 14. Each cam is disposed in complementary relation to a respective brake device, and in the brake released or off position is disposed inthe space provided by a cut-out 10 of washer Q and out of contact with the latter as indicated in FIGURE 4. Upon rotation of device 14 clockwise as viewed in FIGURES 4, 5 and 6, from the disposition indicated in FIGURE 4 to that indicated in FIGURE 5, each cam device contacts a respective resilient brake element 12 and stresses the latter into frictional braking or locking engagement with surface Sf of sleeve S, thus firmly preventing rotation of the sleeve. During this action the limbs of device 14 may yield rearwardly to a small extent. These actions are illustrated on an exaggerated scale in FIGURE Sa. Reverse rotation of device 14 (counterclockwise as viewed in FIGURES 4, 5 and 6) rotates each cam device out of contact with the associated brake element, allowing the latter to spring away from surface S and thus release the sleeve for rotation to adjust the resistor. It will be understood that there are provided slight clearances (such as 0.015"), between Washer Q and sleeve S, and between device 14 and washer Q. The clearances are small and hence it is not feasible to illustrate them accurately in the drawings.

While not necessary to effective operation of the brake or look device of the invention, device 14 is preferably provided with means to facilitate manual rotation thereof by a technician or operator. To that end, the extremity of each Wing 14w is bent forwardly to a desired extent, and is equipped with a grip 14! that may be formed of elastic insulative composition. In the interest of a balanced construction, two diametrically opposed operating grips and wings, and two each of cam devices and brake elements, are provided.

A modified from of brake-applying device is illustrated in FIGURES 7 and 8. Therein a device 114 having depending stud-engaging limbs 114a and 114b is provided with cam devices 114m and HM formed by suitable dimpling of the peripheral edge of the device. A portion below a single actuating arm 114w is cut away to provide stop surfaces 114g, 11411 that are disposed for coaction with the key Qr. As in the principal embodiment of the brake-applying device, the depending limbs are formed to clasp the step portion F of flange F of stud B. Operation and other details of the modified form are either evident from the drawings or from the preceding portion of the specification.

While in the described and illustrated embodiment of the invention the brake element means engages the rear face of a rotatable shell of a knob-enclosed potentiometer it is evident that those means could as well engage the rear face of a different rotary member at the face of a panel. Further, in the light of the present disclosure modifications of the preferred form herein disclosed will become evident to those skilled in the art, and accordingly it is not desired to limit the invention to the illustrated structure except as it is defined by the appended claims.

We claim:

1. For an instrument adapted to be mounted upon and at the face of a panel and having a rotatable knob or like rotatable adjusting means and a stationary mounting stud upon which the rotatable means is supported for rotation and which stud is adapted to be secured in an aperture in the panel, a brake device for securing the adjusting means in adjusted position, comprising:

first means, comprising fixed means restrained from rotation and disposed at the rear of the rotatable adjusting means and arranged to be situated between the adjusting means and the panel upon which the instrument is adapted to be mounted, said fixed means including a resilient brake element movable relative to the fixed means adapted to be pressed forwardly into braking engagement with a rear rotary surface of said adjusting means, and

second means, comprising a rotatable device having a thin generally G-shaped, sheet-like portion adapted to peripherally engage and clasp said stud between the limbs of said portion and rotate thereon between said fixed means and said panel, said device having a cam device on the front face thereof disposed when rotated to force said brake element into frictional engagement with a rear surface of said rotatable adjusting means to secure the latter against rotation.

2. Means as defined by claim 1, said fixed means being of the general character of a washer of resilient material supported by the stud of the instrument and comprising as the brake element a narrow rim portion of the Washer radially separated from the body of the washer but integral therewith.

3. Means as defined by claim 1, said rotatable device having the general character of a resilient retainer having at least one outwardly extending arm arranged to be grasped for manual manipulation.

4. Means as defined in claim 1, said fixed means being of the general character of a flat sheet of resilient material perforated and supported on the supporting stud and comprising as the brake element a narrow circumferentially extending arcuate finger radially separated from the body of the sheet material but integral therewith at one end of the finger and the finger disposed for forward movement into frictional engagement with an adjacent rotary surface of the instrument, and said rotatable device being of sheet material and formed to rotate upon the stud of the instrument rearwardly of said stationary means and having a cam surface thereon disposed when said device is rotated on said stud, to engage and force forwardly the free end of said finger into engagement with said rotary surface.

5. A variable resistor comprising:

first means, including stationary support means having a rear portion of substantially circular cross-section arranged for mounting in an aperture in a panel;

second means, including variable resistor means comprising a rotatable adjusting member supported on said support means forwardly of said rear portion;

third means, including substantially flat sheet-like means disposed on said support means rearwardly of said rotatable adjusting member and having an integral resilient brake element portion constructed and arranged to be flexed forwardly int-o frictional engagement with said rotatable adjusting member; and

fourth means, including a rotatable device supported by said support means rearwardly of said third means and constructed and arranged with cammeans thereon disposed for rotation into and out of contact with said brake element portion to cause flexure of the latter into and out of frictional engagement with said rotatable adjusting member incident to rotation of said rotatable device in respective opposite directions on said support means.

6. A two-piece brake device for an adjustable instrument adjusted by rotation of a knob-like member about the axis of a supporting member, comprising:

a first brake member, comprising a resilient disc-like member fixedly disposed on the supporting member at the rear of the knob-like member and having at least one resilient brake element portion constructed and arranged for flexure axially and for- Wardly into frictional engagement with said knoblike member to inhibit rotation of the latter; and

a brake-actuating member rotatably disposed on said supporting member rearwardly of said first brake member and comprising a cam surface disposed for rotation into and out of contact with said brake element to flex the latter into contact with said knoblike member and to release the latter incident to rotation of the brake-actuating member, said brakeactua-ting member being resilient and of C-shape permitting lateral removal from the supporting member.

7. A variable resistor comprising:

first mean-s, including a stationary support means, constructed with a cylindric portion arranged to be affixed to a panel at an aperture therein and to extend forwardly therefrom;

second means, including a rotary knob-like housing structure adapted to enclose operative components of the resistor and mounted for rotation on said first means and having a rearwardly-facing exposed surface;

third means, consisting essentially of a resilient disclike brake member having at least one resilient brake surface portion disposed closely adjacent to said rearwardly-facing exposed surface and adapted to be resiliently flexed into frictional contact therewith;

and fourth means, including a brake-actuator consisting essentially of a formed piece of resilient material supported on said cylindric portion of said support means for rotation thereon and having cam means constructed and arranged to force said brake surface forwardly into frictional engagement with said rearwardly-facing exposed surface incident to rotation in a predetermined direction on said support means, whereby to frictionally lock said housing in a selected rotational disposition. 8. A variable resistor according to claim 7, said formed piece of resilient material having a C-shaped body portion adapted to snap over said cylindric portion of said support means for rotative support thereon, whereby said brake-actuator may be readily applied to and removed from said support means while the latter is mounted on a panel.

9. A variable resistor device according to claim 7, said brake-actuator comprising a body portion engaging said first means and comprising at least one protruding limb constructed and arranged for easy manual manipulation to effect operation of the brake-actuator. 10. A variable resistor comprising: first means, including a stationary tubular support means constructed and arranged for mounting in an aperture in a panel and adapted for supporting operative parts of the resistor forwardly of the panel;

second means, including a rotatable cylindric housing structure rotatably supported on said support means and adapted for enclosing operative parts of the resistor therein and effective to operate the latter incident to rotation of the housing structure, said housing structure comprising a rearwardly-facing frictional surface;

third means, comprising a disc-like brake member supported by said first means rearward of said housing structure, said member comprising a set of resilient brake elements disposed in close proximity to'said frictional surface for forward stressing into braking engagement with said surface, and means to prevent rotation of said member relative to said first means;

and fourth means, comprising a brake -actautor rotatably mounted on said support means rearwardly of said brake member and comprising a set of cam devices each constructed and arranged to stress forwardly a respective one of said brake elements incident to rotation of the actuator, whereby to cause frictional locking of said housing structure in any rotational position of adjustment.

11. A variable resistor according to claim 10, said brake-actuator comprising a C-shaped body portion arranged to embrace said tubular support means for ready application thereto and removel therefrom.

12. A variable resistor according to claim 10, said brake-actuator including a portion extending radially outward beyond the outline of said housing structure and adapted to bear operating information.

13. A variable resistor according to claim 10, said brake'actuator comprising at least one outwardly and forwardly extending limb constructed and arranged for manual manipulation to rotate the actuator to and from brake-applying positions.

14. A variable resistor according to claim 13, said brake-actuator comprising a C-shaped body portion terminated by portions adapted to closely engage and clasp said tubular support means, whereby said actuator may easily be applied to and removed from the support means.

References Cited by the Examiner UNITED STATES PATENTS 2,509,058 5/50 Haury 338-162 2,739,767 3/56 Dunkelberger et al. l887l X 3,031,035 '4/62 Tomita 188-71 FOREIGN PATENTS 115,201 5/18 Great Britain.

ARTHUR L. LA POINT, Primary Examiner.

PHILIP ARNOLD, Examiner. 

5. A VARIABLE RESISTOR COMPRISING: FIRST MEANS, INCLUDING STATIONARY SUPPORT MEANS HAVING A REAR PORTION OF SUBSTANTIALLY CIRCULAR CROSS-SECTION ARRANGED FOR MOUNTING IN AN APERTURE IN A PANEL; SECOND MEANS, INCLUDING VARIABLE RESISTOR MEANS COMPRISING A ROTATABLE ADJUSTING MEMBER SUPPORTED ON SAID SUPPORT MEANS FORWARDLY OF SAID REAR PORTION; THIRD MEANS, INCLUDING SUBSTANTIALLY FLAT SHEET-LIKE MEANS DISPOSED ON SAID SUPPORT MEANS REARWARDLY OF SAID ROTATABLE ADJUSTING MEMBER AND HAVING AN INTEGRAL RESILIENT BRAKE ELEMENT PORTION CONSTRUCTED AND ARRANGED TO BE FLEXED FORWARDLY INTO FRICTIONAL ENGAGEMENT WITH SAID ROTATABLE ADJUSTING MEMBER; AND 